The present invention relates to methods for producing laser-induced images inside three-dimensional transparent media by using pulsed laser radiation.
A number of techniques for creating a variety of patterns on the surface and inside of transparent substrates using pulsed laser radiation are well known.
The Russian invention No. 321422 to Agadjanov et. al. discloses a method of manufacturing decorative products inside a transparent material by changing the material structure by laser radiation. As disclosed, by moving a material relative to a focused laser beam, it is possible to create a drawing inside the material.
U.S. Pat. No. 3,715,734 to Fajans discloses a three-dimensional memory storage unit, which is prepared by carbonizing selected spots in a block of polymethylmethacrylate by means of a steeply converging laser beam. The energy of the beam is applied in pulses of such duration and at such intensity that carbonization takes place only at the focal point of the beam.
U.S. Pat. No. 4,092,518 to Merard discloses a method for decorating transparent plastic articles. This technique is carried out by directing a pulsed laser beam into the body of an article by successively focusing the laser beam in different regions within the body of the article. The pulse energy and duration is selected based upon the desired extent of the resulting decorative pattern. The effect of the laser is a number of three dimensional xe2x80x9cmacro-destructionxe2x80x9d (fissures in the material of the article) appearing as fanned-out cracks. The pattern of the cracks produced in the article is controlled by changing the depth of the laser beam focus along the length of the article. Preferably, the article is in the form of a cylinder, and the cracks are shaped predominantly as saucer-like formations of different size arranged randomly around the focal point of the optical system guiding a laser beam. The device used to carry out this technique is preferably a multi-mode solid-state, free-running pulse laser used in conjunction with a convergent lens having a focal length from 100 to 200 mm.
U.S. Pat. No. 5,206,496 to Clement et al. discloses a method and apparatus for providing in a transparent material, such as glass or plastic, a mark which is visible to the naked eye or which may be xe2x80x9cseenxe2x80x9d by optical instruments operating at an appropriate wavelength. The Clement et al. Patent describes a method and apparatus for producing a subsurface marking which is produced in a body such as bottle, by directing into the body a high energy density beam and bringing the beam to focus at a location spaced from the surface, so as to cause localized ionization of the material. In the preferred embodiment the apparatus includes a laser as the high energy density beam source. The laser may be a Nd-YAG laser that emits a pulsed beam of laser radiation with a wavelength of 1064 nm. The pulsed beam is incident upon a first mirror that directs the beam through a beam expander and a beam combiner to a second mirror. A second source of laser radiation in the form of a low power He-Ne laser emits a secondary beam of visible laser radiation with a wavelength of 638 m. The secondary beam impinges upon the beam combiner where it is reflected toward the second reflecting surface coincident with the pulsed beam of laser radiation from the Nd-YAG laser. The combined coincident beams are reflected at the reflecting surface via reflecting two other surfaces to a pair of movable mirrors for controlling movement of the beam. The beam then passes through a lens assembly into the body to be marked.
Soviet patent publication 1838163 to P. V. Agrynsky, et. al discloses a process for forming an image in a solid media by processing of the optically transparent solid material by a beam of radiation with changeable energy for creation of the image.
WIPO Patent Document No. 96/30219 to Lebedev discloses a technology for creating two- or three-dimensional images inside a polymer material using penetrating electromagnetic radiation. The technology can be used for marking and for producing decorative articles and souvenirs. Specifically, laser radiation is used as the penetrating radiation, and carbonizing polymers are used as the polymer material. By these means, it is possible to produce both black and half-tone images in the articles.
U.S. Pat. No. 5,575,936 to Goldfarb discloses a process and apparatus where a focused laser beam causes local destruction within a solid article, without effecting the surface thereof. The apparatus for etching an image within a solid article includes a laser focused to a focal point within the article. The position of the article with respect to the focal point is varied. Control means, coupled to the laser, and positioning means are provided for firing the laser so that a local disruption occurs within the article to form the image within the article.
U.S. Pat. No. 5,637,244 to Erokhin discloses a technique which depends on a particular optical system including a diffraction limited Q-switched laser (preferably a solid-state single-mode TEM00) aimed into a defocusing lens having a variable focal length to control the light impinging on a subsequent focusing lens that refocuses the laser beam onto the transparent article being etched. The laser power level, operation of the defocusing lens, and the movement of the transparent article being etched are all controlled by a computer. The computer operates to reproduce a pre-programmed three-dimensional image inside the transparent article being etched. In the computer memory, the image is presented as arrays of picture elements on various parallel planes. The optical system is controlled to reproduce the stored arrays of picture elements inside the transparent material. A method for forming a predetermined half-tone image is disclosed. Accordance to the method, microdestructions of a first size are created to form a first portion of the image and microdestruction of a second size different from the first size are created to form a second portion of the image. Different sizes of microdestructions are created by changing the laser beam focusing sharpness and the radiation power thereof before each shot.
U.S. Pat. No. 5,653,900 to Clement, et al. discloses a method and an apparatus for making a moving body of material. In a preferred embodiment, the apparatus includes at least one movable galvanometer mirror capable of moving the laser beam to create a mark of a predetermined shape.
U.S. Pat. No. 5,886,318 to A. Vasiliev and B. Goldfarb discloses a method for laser-assisted image formation in transparent specimens, which consists in establishing a laser beam having different angular divergence values in two mutually square planes. An angle between the plane with a maximum laser beam angular divergence and the surface of the image portion being formed is changed to suit the required contrast of an image.
EPO Patent Document 0743128 to Balickas et al. disclose a method of marking products made of transparent materials which involves concentration of a laser beam in the material which does not absorb the beam, at a predetermined location, destruction of the material by laser pulses and formation of the marking symbol by displacement of the laser beam. Destruction of the material at that location takes place in two stages. In the first stage, the resistance of the material to laser radiation is altered, while, in the second stage, destruction of the material takes place at that location.
Russian patent publication RU 20082288 to S. V. Oshemkov discloses a process for laser forming of images in solid media by the way of focusing of laser radiation in a point inside a sample which differs by following: with the aim to save the surface and the volume of the sample before the definite point and creation of three dimensional images, the sample is illuminated with the power density higher than the threshold of volume breakdown and moving the sample relatively to the laser beam in three orthogonal directions.
U.S. Pat. No. 6,087,617 to Troitski et al. discloses a computer graphic system for producing an image inside optically transparent material. An image reproducible inside optically transparent material by the system is defined by potential etch points, in which the breakdowns required to create the image in the selected optically transparent material are possible. The potential etch points are generated based on the characteristics of the selected optically transparent material. If the number of the potential etch points exceeds a predetermined number, the system carries out an optimization routine that allows the number of the generated etch points to be reduced based on their size. To prevent the distortion of the reproduced image due to the refraction of the optically transparent material, the coordinates of the generated etch points are adjusted to correct their positions along a selected laser beam direction.
U.S. Pat. No. 6,333,486 to Troitski discloses method and laser system for creation of laser-induced damages to produce high quality images. Accordance to the invention, a laser-induced damage is produced by simultaneously generating breakdowns in several separate focused small points inside the transparent material area corresponding to this etch point. Damage brightness is controlled by variation of a number of separate focused small points inside the transparent material area.
U.S. Pat. No. 6,417,485 to Troitski discloses method and laser system controlling breakdown process development and space structure of laser radiation for production of high quality laser-induced damage images. Accordance to the invention, at the beginning an applied laser radiation level just exceeds an energy threshold for creating a plasma condition in the material, and thereafter the energy level of the applied laser radiation is just maintain the plasma condition. Accordance to another method a laser generates a TEMmn radiation. The values of the integers m and n are controlled and determined so as to reproduce particular gray shades for a particular point of an image.
U.S. Pat. No. 6,399,914 to Troitski discloses methods and an apparatus for creating high quality laser-induced damage images. One or more embodiments of the invention comprise a method for producing laser-induced damage images inside the special transparent material containing special kinds of impurities, which decrease the damage threshold of the material. Colored laser-induced damage images are produced inside transparent materials containing color impurities. Laser radiation is focused inside the transparent material in such a way that focal area contains at least one said impurity. Other embodiments of the invention comprise a method and a system for producing laser-induced images by using two lasers. The first laser generates radiation, which heats the predetermined material area about a point, where breakdown should be produced, to the vitrify temperature. The second laser generates radiation, which creates breakdown in a point of the heated area after the area is heated to the vitrify temperature.
U.S. Pat. No. 6,426,480 to Troitski discloses the method and laser system for production of high quality single-layer laser-induced damage portraits inside transparent material.
U.S. patent application Ser. No. 10/117,592 to Troitski et al. discloses the method for producing images containing laser-induced color centers and laser-induced damages. These color centers are produced in a result of photoionization generated by laser radiation with energy lower the breakdown threshold.
U.S. patent application Ser. No. 09/354,236 to Troitski discloses the laser-computer graphic system for generating portrait and 3-D sculpture reproductions inside optically transparent material.
U.S. patent application Ser. No. 09/354,236 to Troitski et al discloses the method and laser system for generating laser radiation of specific temporal shape for production of high quality laser-induced damage images.
U.S. patent application Ser. No. 09/679,201 to Troitski discloses the method and laser system for production of high-resolution laser-induced images inside transparent materials by generating small etch points.
U.S. patent application Ser. No. 10/016,013 to Troitski discloses the method for production of laser-induced damage images with special characteristics by creating damages of special space shape.
U.S. patent application Ser. No. 09/354,236 to Troitski et al. discloses the method creating damage arrangement for production of 3D laser-induced damage portraits inside transparent materials.
U.S. patent application Ser. No 29/164,228 to Troitski shows the ornamental design for transparent material inside of which a 2D laser-induced damage portrait is placed.
U.S. patent application Ser. No 29/165,478 to Troitski and Cashman shows the ornamental design for transparent material inside of which a 2D laser-induced damage portrait is placed on a spherical surface.
The publication xe2x80x9cSystem for creation of laser-induced damage images and problems of their optimizationxe2x80x9d (I. N. Troitski, Proc. of SPIE Vol. 3902 (2000), 489-499) describes methods for generating 3D images and portraits allowing reproduction of them within an optically transparent material with the same resolution like computer images, without sharp point structure and without significant fluctuation of gray shades.
The publication xe2x80x9cExperience of creation of laser-induced damage imagesxe2x80x9d (I. N. Troitski, Proc. of SPIE Vol. 3902 (2000), 479-488) discloses the specific system for production of laser-induced damage images.
The publication xe2x80x9cImage recording by laser-induced damagesxe2x80x9d (I. N. Troitski, Optical Memory and Neural Networks, Vol. 9, No. 4, (2000) 233-238) discusses the problems of laser-induced damage utilization for image recording.
The publication xe2x80x9cMethod and laser system for creating high-resolution laser-induced damage imagesxe2x80x9d (I. N. Troitski, Proc. of SPIE Vol. 4679 (2002), 392-399) describes creation of small laser-induced damages without large star structure by the specific temporal radiation.
As it is possible to conclude from the review of Patents and scientific publications, the laser-induced image technology combines progress in the fields of:
the interaction of power laser radiation with transparent material, the laser engineering and the computer graphic art.
New researches of the interaction of power laser radiation with transparent material give the information for development of methods for creating etch points with special characteristics, letting to produce high quality laser-induced images. Evolution of the laser engineering gives a chance to realize the methods and create modern, high-speed production laser systems. The progress in the computer graphic art enables to develop new methods for processing and transformation of displayed images into the form suitable for image production inside three-dimensional transparent media
Although these fields are very different, the production of laser-induced images demands to take into account results of each field. So it is impossible to transfer displayed image into aggregate of etch points without taking into account peculiar properties of the interaction of power laser radiation with transparent material.
The present invention is based on the features of the interaction of power laser radiation with transparent material and the progress of the computer graphic art. One of its purposes is creation of a method for transformation of both the displayed image represented by incomplete data, and the new image parts added during production, into aggregate of laser-induced damages (etch points) so as the high quality laser-induced image can be produced.
The present invention has its principal task to provide a method for the production of complicated laser-induced images inside transparent material and more particularly, of the images about which complete information is lacking before production and is only added during production.
One or more embodiments of the invention comprise a method for detachment of the image parts, about which we do not have information, so as the new parts can be produced within a transparent material after the production of the rest parts without internal split of the material.
Another embodiment of the invention is a method for concordance of the space resolution of the new image part with the space resolution of the whole image by smoothing of the average density of laser-induced damages.
One or more embodiments of the invention comprise a method for adaptation of a contour of the new image part to the corresponding detachment line.
One or more embodiments of the invention comprise a method for elimination of objectionable visual effect connected with the increase of laser-induced damages density of the detachment area.
One or more embodiments of the invention comprise a method for smoothing of gray shades along the borders between new image parts and the adjacent areas of the whole images without destruction of gray shade information.
One or more embodiments of the invention comprise a method for concordance of the new image layers with the layers of the whole image.
One or more embodiments of the invention comprise a method for simultaneous processing and production of the new image parts and an original image, represented by incomplete data.